I've had things like this happen when OC'ing.
(I have the P4C800-E Deluxe rev 2.0 btw)
Things start "dissapearing" from the hardware panel but without causing errors at extreme FSB's.
On my board the onboard sounds system disappears at 247FSB.
At 254 the onboard NIC goes AWOL.
And at 260+ the SATA RAID controller craps out.
Now here's the interesting bit:
Your USB 2.0 ports are actually identified as 2 devices.
An "USB Universal Host controller" (multiple may be listed)
and an "USB2 Enhanced Host controller"
If the "USB2 Enhanced Host controller" craps out but the others don't your USB 2.0 port is now a USB 1.1 port.
I didn't turn anything off in the BIOS either, they simply dissappear.
And not only in Windows either, when the mobo is booting up and its displaying a list of devices, they are gone there too.
Congrats to Intel and Asus for actually having components "drop dead" at OC'ed speeds instead of crashing the whole board.
[EDIT] 3.12/2.6=1.2 > 200*1.2=240FSB
A 240FSB sounds about right for these boards to start acting funny without custom cooling.
I'm running 250FSB right now. Good thing I don't need the onboard sound.